I like 2 PSI in most of my tires..especially on the rocky trails to avoid puncture. But when you run this low it's really important to keep the rear tires extactly the same..the torque of acceleration will cause the machine to steer in the direction of the lower tire. The more torque the machine has the worst the effect!!
If you put 5 PSI in one and 2 PSI in the other on your TRI-Z or 250R and run it you'll see what I mean..it may vary from one tire to another more!
There are low pressure gauges that go from 0-15 on the market..I bought a handful of them on Ebay a few years back and keep them on all my boxes.
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)